Microprocessor based controllers have been developed in recent years to assist in the preparation of properly cooked foods. Typically, such controllers, among other things, regulate the temperature within the cooking appliance to insure that the food is cooked or baked to the proper degree of doneness. Advantageously, such controllers may use intelligent sensing and diagnostics built into the cooking appliance and coupled through an interface board to detect and identify various types of failures. See, for example, U.S. Pat. No. 5,043,860 and applicants' copending application U.S. Ser. No. 08/501211, entitled "Multiprobe Intelligent Diagnostic System For Food-Processing Apparatus" which are commonly assigned and incorporated herein by reference.
While these so-called "smart interface" boards perform excellently, they generally require the use of multiple sensors. Accordingly, although these "smart interface" boards are well-suited for modern cooking appliances, they are ill-suited for the hundreds of thousands of cooking appliances manufactured over the last twenty years that use single temperature sensors. While retrofitting these older cooking appliances with additional sensors and interface boards would solve the problem, the associated cost makes it prohibitively expensive to do so.
Accordingly, what is needed is a simple and low cost diagnostic system to diagnose that certain physical characteristics of the cooking appliance are not working properly--all without the need of special sensors and interface boards.
Also, any variation in one or more of the cooking parameters alters the quality of the cooked food product, which may pose health risks. To ensure that the food product is cooked properly, it would be further desirable to provide a method and diagnostic system for monitoring the cooking operation of the appliance which readily detects such variations in an objective manner.